In the manufacturing of semiconductor devices, it is well known to form isolation regions that electrically isolate the various active regions present within the device from each other. One method of electrically isolating the active device regions is to form a trench isolation region between adjacent devices. Such prior art trench isolation regions typically comprise a trench that is formed within the substrate and filled with a dielectric material such as SiO.sub.2.
Three types of trench isolation regions are known: including shallow trenches (trenches whose depth is less than about 1 .mu.m), moderate trenches (trenches whose depth is from about 1 to about 3 .mu.m), and deep trenches (trenches whose depth is greater than 3 .mu.m).
Shallow trench isolation (STI) regions are the choice of device isolation used in bipolar technologies. Despite this, the presence of STI regions in bipolar devices has some drawbacks associated therewith. In particular, it is well known that bipolar pipe yield can be affected by dislocations originating at the corner of the STI region. This problem has been shown to be caused by the stress in the isolation trench due to over oxidation during the semiconductor processing.
Several approaches have been attempted in order to reduce the stress problem in the STI region. Some of the more common prior art attempts for reducing stress include: reducing the amount of oxidation in the trench as well as reducing the level of Si interstitials at the base of the STI using a sink such as C implants. Others have shown that stress in the trench may be reduced by relaxation of the tetraethylorthosilicate (TEOS) trench dielectric material thru high temperature anneals.
To date, no effective method is known which is capable of substantially reducing the stress in the trench isolation region. As such, there is a continued need for developing a new and improved method that can adequately reduce the stress of the trench isolation region caused by over oxidation during the manufacturing of the semiconductor device. Such a method would represent a significant advancement in the art since it would lead to increase bipolar pipe yield.